LXR linux/include/linux/posix-clock.h

   1/*
   2 * posix-clock.h - support for dynamic clock devices
   3 *
   4 * Copyright (C) 2010 OMICRON electronics GmbH
   5 *
   6 *  This program is free software; you can redistribute it and/or modify
   7 *  it under the terms of the GNU General Public License as published by
   8 *  the Free Software Foundation; either version 2 of the License, or
   9 *  (at your option) any later version.
  10 *
  11 *  This program is distributed in the hope that it will be useful,
  12 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 *  GNU General Public License for more details.
  15 *
  16 *  You should have received a copy of the GNU General Public License
  17 *  along with this program; if not, write to the Free Software
  18 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19 */
  20#ifndef _LINUX_POSIX_CLOCK_H_
  21#define _LINUX_POSIX_CLOCK_H_
  22
  23#include <linux/cdev.h>
  24#include <linux/fs.h>
  25#include <linux/poll.h>
  26#include <linux/posix-timers.h>
  27#include <linux/rwsem.h>
  28
  29struct posix_clock;
  30
  31/**
  32 * struct posix_clock_operations - functional interface to the clock
  33 *
  34 * Every posix clock is represented by a character device. Drivers may
  35 * optionally offer extended capabilities by implementing the
  36 * character device methods. The character device file operations are
  37 * first handled by the clock device layer, then passed on to the
  38 * driver by calling these functions.
  39 *
  40 * @owner:          The clock driver should set to THIS_MODULE
  41 * @clock_adjtime:  Adjust the clock
  42 * @clock_gettime:  Read the current time
  43 * @clock_getres:   Get the clock resolution
  44 * @clock_settime:  Set the current time value
  45 * @open:           Optional character device open method
  46 * @release:        Optional character device release method
  47 * @ioctl:          Optional character device ioctl method
  48 * @read:           Optional character device read method
  49 * @poll:           Optional character device poll method
  50 */
  51struct posix_clock_operations {
  52        struct module *owner;
  53
  54        int  (*clock_adjtime)(struct posix_clock *pc, struct timex *tx);
  55
  56        int  (*clock_gettime)(struct posix_clock *pc, struct timespec64 *ts);
  57
  58        int  (*clock_getres) (struct posix_clock *pc, struct timespec64 *ts);
  59
  60        int  (*clock_settime)(struct posix_clock *pc,
  61                              const struct timespec64 *ts);
  62
  63        /*
  64         * Optional character device methods:
  65         */
  66        long    (*ioctl)   (struct posix_clock *pc,
  67                            unsigned int cmd, unsigned long arg);
  68
  69        int     (*open)    (struct posix_clock *pc, fmode_t f_mode);
  70
  71        __poll_t (*poll)   (struct posix_clock *pc,
  72                            struct file *file, poll_table *wait);
  73
  74        int     (*release) (struct posix_clock *pc);
  75
  76        ssize_t (*read)    (struct posix_clock *pc,
  77                            uint flags, char __user *buf, size_t cnt);
  78};
  79
  80/**
  81 * struct posix_clock - represents a dynamic posix clock
  82 *
  83 * @ops:     Functional interface to the clock
  84 * @cdev:    Character device instance for this clock
  85 * @dev:     Pointer to the clock's device.
  86 * @rwsem:   Protects the 'zombie' field from concurrent access.
  87 * @zombie:  If 'zombie' is true, then the hardware has disappeared.
  88 *
  89 * Drivers should embed their struct posix_clock within a private
  90 * structure, obtaining a reference to it during callbacks using
  91 * container_of().
  92 *
  93 * Drivers should supply an initialized but not exposed struct device
  94 * to posix_clock_register(). It is used to manage lifetime of the
  95 * driver's private structure. It's 'release' field should be set to
  96 * a release function for this private structure.
  97 */
  98struct posix_clock {
  99        struct posix_clock_operations ops;
 100        struct cdev cdev;
 101        struct device *dev;
 102        struct rw_semaphore rwsem;
 103        bool zombie;
 104};
 105
 106/**
 107 * posix_clock_register() - register a new clock
 108 * @clk:   Pointer to the clock. Caller must provide 'ops' field
 109 * @dev:   Pointer to the initialized device. Caller must provide
 110 *         'release' field
 111 *
 112 * A clock driver calls this function to register itself with the
 113 * clock device subsystem. If 'clk' points to dynamically allocated
 114 * memory, then the caller must provide a 'release' function to free
 115 * that memory.
 116 *
 117 * Returns zero on success, non-zero otherwise.
 118 */
 119int posix_clock_register(struct posix_clock *clk, struct device *dev);
 120
 121/**
 122 * posix_clock_unregister() - unregister a clock
 123 * @clk: Clock instance previously registered via posix_clock_register()
 124 *
 125 * A clock driver calls this function to remove itself from the clock
 126 * device subsystem. The posix_clock itself will remain (in an
 127 * inactive state) until its reference count drops to zero, at which
 128 * point it will be deallocated with its 'release' method.
 129 */
 130void posix_clock_unregister(struct posix_clock *clk);
 131
 132#endif
 133